Navigation backBarButtonItem 設置

根據蘋果官方指出：backbarbuttonItem不能定義customview，所以，只能貼圖或者，讓leftBarButtonItem變成自定義返回按鈕，自己寫個方法進行[self.navigationController   pop當前Item

之前大家是否疑惑爲什麼設置了類似這樣的代碼
UIBarButtonItem *backButton = [[UIBarButtonItem alloc]

                                                                  initWithTitle:"返回" 

                                                                  style:UIBarButtonItemStylePlain 

                                                                  target:self 

                                                                  action:nil];

self.navigationItem.backBarButtonItem = backButton;
複製代碼界面上backButton並沒出現“返回”的字樣

其實是被leftBarButtonItem和rightBarButtonItem的設置方法所迷惑了
lleftBarButtonItem和rightBarButtonItem設置的是本級頁面上的BarButtonItem，而backBarButtonItem設置的是下一級頁面上的BarButtonItem
比如：兩個ViewController，主A和子B，我們想在A上顯示“刷新”的右BarButton，B上的BackButton顯示爲“撤退”
就應該在A的viewDidLoad類似方法中寫：
UIBarButtonItem *refreshButton = [[UIBarButtonItem alloc]

                                                                  initWithTitle:"刷新"